Tag Archives: Hematology

Factor VIII activity can be measured in different ways. Two of the assays used to assess the Factor VIII activity are the one-stage clotting assay and the chromogenic assay. The one-stage clotting assay is still the most widely used. The one stage clotting assay measures the extent a plasma sample corrects the coagulation time of …Continue Reading

Currently the global test used to detect intrinsic factor deficiencies in patients with bleeding is the activated partial thromboplastin time (APTT). The APTT reagent used should be sensitive to a reduction in coagulation factors such as FVIII and FIX that are commonly associated with bleeding. Literature states that it is desirable to have APTT systems …Continue Reading

Von Willebrand Disease (VWD) is a genetic disorder caused by missing or defective von Willebrand factor (VWF), a clotting protein. VWF binds factor VIII, a key clotting protein, and platelets in blood vessel walls, which help form a platelet plug during the clotting process. [1] History of the disease The first written piece describing this inherited …Continue Reading

Using Factor VIII Deficient Plasma from a human donor with a congenital deficiency is preferred to using an artificial immunodepleted Factor VIII substrate. There are several aspects that make congenital factor deficient plasma preferable to immunodepleted. The immunodepletion process During the immunodepletion process, not only is the Factor VIII removed, but the vonWillebrand factor is …Continue Reading

Laboratories use normal reference ranges (NRRs) to identify whether a test result is within the normal range or outside this range (and to thus identify an abnormal result). The relative false positive to true positive rate increases substantially for rare disorders and is a particular problem with congenital disorders such as protein C, protein S, …Continue Reading

A physician may order mixing studies when a patient’s prothrombin time (PT), activated partial thromboplastin time, (aPTT) or both PT and aPTT are prolonged outside the upper limit of the laboratory’s established normal range. Determining the cause of the prolongation It is important to determine if the cause of the prolongation is due to a …Continue Reading